Telephony has, over the past century, become ubiquitous in developed countries around the world. What, for many years, was a communication technology that required physical, wired connections has evolved into a communication technology that includes many modes of communication, many of which include wireless connections. The cellular telephony industry was the first to offer mobile communication to customers who wished to be reachable by telephone while away from physical, wired connections.
Recent developments and standardization efforts have led to an increase in availability of wireless data networks. While the current wireless data networks do not offer the many-square-kilometer coverage areas that cellular base stations offer, the wireless access points that provide wireless data network services offer many-square-meter coverage areas. The coverage areas offered by wireless access points have been found to be suitable for users situated in cafés, airports and other public places.
In parallel with the developments in wireless networking, there have been advances in quality and acceptance of data network telephony, for instance, using the Internet. The Internet Engineering Task Force (IETF) has published a Request for Comments (RFC) numbered 3261 (see www.ietf.org) for a protocol called the “Session Initiation Protocol” or “SIP”. SIP is an application-layer control protocol that can be used to establish, modify and terminate multimedia sessions (conferences) such as Internet telephony calls. Internet telephony applications are typically executed on desktop or laptop computers. However, as handheld computing devices, such as personal digital assistants (PDAs), have gained in processor power and added wireless networking capabilities, consequently, new applications have been developed to exploit their wireless networking capabilities and processing power. One such application is Internet telephony.
Many PDAs have cellular telephone capabilities. Where a device has cellular telephone capabilities (a first mode) and wireless data networking/Internet telephony capabilities (a second mode), the device may be called a dual-mode mobile terminal. Increasingly, a user of a dual-mode mobile terminal may find that both a cellular telephone network and a wireless data network are available at a given place and time. The user may consider that airtime used in placing a telephone call using the cellular telephone network may, for instance, be charged per minute. In contrast, often airtime in a wireless data network is provided freely, to encourage patronage close to the access point, say, where the access point has been established in a café or in an airport. At the given place and time, the user may wish to simply place a call, without having to configure the dual-mode mobile terminal to use one mode or another.
A method for performing presence-based call switching would be desirable.